Efforts to improve adherence to highly active antiretroviral therapy (HAART) regimens are critical for improving clinical outcomes in HIV-infected patients and reducing costly utilization of hospitalizations, emergency department and urgent care visits. Little data exists on the influence of healthcare system level and provider care team characteristics on HAART adherence. Our previous research demonstrates that HIV clinical pharmacists contribute to significant improvements in adherence and clinical parameters and reductions in health care utilization. We hypothesize those services provided by other members of HIV multidisciplinary care teams (HIV specialty provider, nurse manager/care coordinator, mental health worker, social worker, health educator, and nutritionist) may also contribute to these outcomes. We propose an innovative analytic approach by performing a retrospective cohort analysis of HIV multidisciplinary care teams in Kaiser Permanente California ("KP") utilizing our HIV registry of over 22,000 HIV-infected patients in the HAART era (i.e., 1997-2007). There are 26 KP medical centers offering HIV care, with varying multidisciplinary team composition. We will investigate the association of the components of the HIV multidisciplinary care team in achieving maximal antiretroviral adherence through 24 months upon initiation of a HAART regimen. Next, we will use classification and regression trees to determine which components of the team in combination are associated with maximal HAART adherence. We will test whether teams identified as promoting maximal adherence also are associated with optimization of HIV clinical parameters and reduction in inpatient and outpatient urgent care visit utilization. Study innovations and strengths include our unique access to large patient databases encompassing patient, provider, and medical center level data including clinical outcomes and important patient level covariates (for example HIV risk behavior), stable and extended follow-up of our patient population, and our capability to capture and measure multidisciplinary care team data that varies across medical centers and time. Study results will inform the relative impact of the components of multidisciplinary care team on HAART adherence and the optimized composition of an HIV multidisciplinary care team for maximal HAART adherence, which is generalizable to both public and private HIV clinical care settings to offer more evidence-based comprehensive HIV care services. This proposal is innovative in its consideration of optimizing HIV multi-disciplinary care teams in combination, and the use of regression tree analysis to determine optimized HIV multi-disciplinary care team composition. This approach will help inform HIV care clinics on the most requisite team members for optimal HAART adherence and outcome measures, and will guide development of a future RCT of an optimal HIV multidisciplinary care model. PUBLIC HEALTH RELEVANCE: Today, HIV care like other complex, chronic conditions requires multiple care services for optimal outcomes. Little is understood about how comprehensive HIV services provided by multidisciplinary care team members may influence how well patients follow treatment recommendations. This study is important because high levels of patient adherence to HIV medications are critical to achieving good clinical outcomes, and may be more likely achieved when particular types of multidisciplinary care services are offered, whether singularly or in particular combinations. Findings from this research will help to inform how best to allocate public and private clinic resources for providing comprehensive HIV care.